Hello- last winter, my northwest bedroom walls were so cold, there was frost on the inside wall. some water running down etc... I could tell from the touch that perhaps one or several cavities were probably without insulation, yet when I removed the plug plate, I could not push a coathanger into the wall with out hitting insulation. Another was clearly without insulation. I have to do something. Can I safely add blow in foam to the wall with fiberglass batts ? I am thinking of cutting a 6 " horizontal strip of drywall out to get a better picture of the interior cavity wall. I can repair the wall-I am sure- (wainscoating, beadboard etc) Would it be ok to just blow the foam in, or should I remove any fiberglass that might be in there and has collapsed.? Thank you for your help.